My question is generally about adding elsarticle document class to TeXStudio.
In the installation documents it says that I should download .ins and .dtx files and compile them with latex. I don't know ...

I am using the elsevier journal article format. The problem is I am using the amsthm, amsmath packages but still getting environment proof, theorem undefined kind of error. what to do ?
For the usual ...

Images are coming after the references (due to confidentiality i cannot upload the code or snapshots).
I am using the elsarticle in documentclass with 2 columns.
Using Multicols package.
used [!ht] ...